Some conventional printing devices for printing images on recording paper have been provided with a photosensor for detecting printing results on the recording paper. The results picked up by the photosensor can be used to detect problems in the printing state, such as printing that is faint or patchy. If the printing problems are due to a shortage of ink or the like, the printing device will eventually stop printing due to a lack of ink if no steps are taken. Therefore, the device notifies the user of the problem when the photosensor detects a problem in the printing state. In this way, the user can take steps to restore the printing state, such as replacing the ink tanks or ink ribbon, before the printing device loses its ability to print.